Dual-sided wafer imaging apparatus and methods thereof

Abstract

The present disclosure provides a dual-sided wafer imaging apparatus and methods thereof. The dual-sided wafer imaging apparatus includes one or more load ports, one or more mechanical arms for transporting a wafer, a wafer transfer stage, a first line scan camera mounted below the wafer transfer stage, a second line scan camera mounted above the wafer transfer stage, a first optical lens mounted on the first line scan camera, a second optical lens mounted on the second line scan camera, and line light sources respectively mounted below and above the wafer transfer stage. The load ports are configured for an automated load operation or unload operation of a wafer pod of an automated transport equipment. The wafer transfer stage includes vacuum suction points in contact with a backside of the wafer, and the wafer transfer stage further includes a drive motor producing a linear reciprocating motion for moving the wafer.

What is claimed is: 
     
       1. A dual-sided wafer imaging apparatus, comprising:
 one or more load ports for an automated load operation or unload operation of a wafer pod of an automated transport equipment; 
 one or more mechanical arms for transporting a wafer; 
 a wafer transfer stage comprising three or more vacuum suction points in contact with a backside of the wafer for retaining the wafer on the wafer transfer stage in a vacuuming manner, the wafer transfer stage further comprising a drive motor producing a linear reciprocating motion for moving the wafer, wherein the mechanical arm is actuated for transporting the wafer from the load port to the wafer transfer stage; 
 a first line scan camera mounted below the wafer transfer stage; 
 a second line scan camera mounted above the wafer transfer stage; 
 a first optical lens mounted on the first line scan camera for capturing a backside wafer image of the wafer; 
 a second optical lens mounted on the second line scan camera for capturing a frontside wafer image of the wafer; 
 two or more line light sources respectively mounted below and above the wafer transfer stage; and 
 a wafer aligner located below the wafer and being actuated to move along a vertical direction for adjusting a position and a rotation angle of the wafer, returning the wafer to an origin point, and reading a label. 
 
     
     
       2. The dual-sided wafer imaging apparatus of  claim 1 , wherein the two or more line light sources are aligned with each other and output a yellow light or a white light. 
     
     
       3. The dual-sided wafer imaging apparatus of  claim 1 , wherein the first line scan camera and the second line scan camera are actuated at the same time for capturing the backside wafer image and the frontside wafer image as a dual-sided image of the wafer at the same time. 
     
     
       4. The dual-sided wafer imaging apparatus of  claim 1 , further comprising an air injection device comprising a first nozzle aligned with the first optical lens of the first line scan camera, wherein the first nozzle is arranged to generate a first air stream toward the first optical lens for preventing particles from adhering to the first optical lens. 
     
     
       5. The dual-sided wafer imaging apparatus of  claim 4 , the air injection device further comprising a second nozzle aligned with the second optical lens of the second line scan camera, wherein the second nozzle is arranged to generate a second air stream toward the second optical lens for preventing particles from adhering to the second optical lens. 
     
     
       6. The dual-sided wafer imaging apparatus of  claim 5 , wherein the first and second nozzles are actuated to generate the first and second air streams toward the first and second optical lenses respectively when the wafer is not being imaged that is the first and second first and second live scan cameras are not in use. 
     
     
       7. A method for dual-sided imaging of a wafer, comprising the steps of:
 retaining the wafer on a wafer transfer stage in a vacuuming manner, wherein the wafer transfer stage has three or more vacuum suction points in contact with a backside of the wafer to suck the wafer on the wafer transfer stage; 
 capturing a dual-sided image of the wafer, wherein when the wafer is transferred in an outbound trip by the wafer transfer stage, a first line scan camera and a second line scan camera respectively mounted below and above the wafer transfer stage respectively capture a first backside wafer image and a frontside wafer image of the dual-sided image of the wafer; 
 rotating the wafer by a predetermined angle, wherein when the wafer reaches an end point of the outbound trip, a wafer aligner located below the wafer is actuated to move along a vertical direction to pick up the wafer, rotate the wafer by the predetermined angle, and return the wafer to the wafer transfer stage; 
 capturing a second backside wafer image, wherein when the wafer is transferred in a return trip by the wafer transfer stage, the first line scan camera below the wafer transfer stage captures the second backside wafer image; and 
 performing an image processing operation, wherein one or more regions occluded by one or more contact points in the first backside wafer image are imaged more clearly by replacing the first backside wafer image with the second backside wafer image. 
 
     
     
       8. The method of  claim 7 , wherein two or more line light sources are respectively mounted below and above the wafer transfer stage and are aligned with each other, wherein the two or more line light sources output a yellow light or a white light. 
     
     
       9. The method of  claim 7 , further comprising a step of via a first nozzle, generating a first air stream toward the first optical lens for preventing particles from adhering to the first optical lens, wherein the first nozzle is aligned with the first optical lens of the first line scan camera. 
     
     
       10. The method of  claim 9 , further comprising a step of via a second nozzle, generating a second air stream toward the second optical lens for preventing particles from adhering to the second optical lens, wherein the second nozzle is aligned with the second optical lens of the second line scan camera. 
     
     
       11. The method of  claim 10 , wherein the first and second nozzles are actuated to generate the first and second air streams toward the first and second optical lenses respectively when the wafer is not being imaged that is the first and second first and second live scan cameras are not in use. 
     
     
       12. A method for dual-sided defect inspection and classification of a wafer, comprising the steps of:
 via a first line scan camera and a second line scan camera, capturing a backside wafer image and a frontside wafer image as a dual-sided image of the wafer on a wafer transfer stage, wherein a first optical lens of the first line scan camera and a second optical lens of the second line scan camera are mounted below and above the wafer transfer stage for capturing the backside wafer image and the frontside wafer image respectively; 
 determining whether a deep learning object detection model is available; 
 when the deep learning object detection model is available, feeding each of the backside wafer image and the frontside wafer image to be inspected into the deep learning object detection model and outputting a plurality of output data, wherein each output data comprises a predicted probability, a predicted classification, and a predicted frame position of a defect in the image; 
 filtering out data having a predicted probability lower than a preset threshold value; 
 selecting, by using a non-maximum suppression algorithm, an optimal predicted frame from a plurality of predicted frames having an intersection over union greater than the preset threshold value; 
 calculating a defect characteristic value according to the predicted classification and the predicted frame position; and 
 outputting an inspection result of the frontside wafer image and the backside wafer image. 
 
     
     
       13. The method of  claim 12 , further comprising the steps of:
 when the deep learning object detection model is not available, labeling a plurality of wafer images as a training data and marking a position and a classification of each defect in the wafer images, wherein the defect position is represented by a square frame surrounding the defect, and image coordinates of the upper left and bottom right vertices of the square frame are recorded; and 
 training the deep learning object detection model, wherein a predetermined quantity of the training data is used to train the deep learning object detection model. 
 
     
     
       14. The method of  claim 12 , wherein two or more line light sources are respectively mounted below and above the wafer transfer stage to align with each other, and the two or more line light sources output a yellow light or a white light. 
     
     
       15. The method of  claim 14 , before the step of capturing the backside wafer image and the frontside wafer image, further comprising a step of via a first nozzle, generating a first air stream toward the first optical lens for preventing particles from adhering to the first optical lens, wherein the first nozzle is aligned with the first optical lens of the first line scan camera. 
     
     
       16. The method of  claim 15 , before the step of capturing the backside wafer image and the frontside wafer image, further comprising a step of via a second nozzle, generating a second air stream toward the second optical lens for preventing particles from adhering to the second optical lens, wherein the second nozzle is aligned with second first optical lens of the first line scan camera. 
     
     
       17. The method of  claim 16 , wherein the first and second nozzles are actuated to generate the first and second air streams toward the first and second optical lenses respectively when the wafer is not being imaged that is the first and second first and second live scan cameras are not in use.